1. Field of the Invention
The present invention relates to the field of sensor technology and, in particular, to the formation of hermetically sealed substrates used for sensing a variety of parameters, including physiological parameters.
2. Description of Related Art
The combination of biosensors and microelectronics has resulted in the availability of portable diagnostic medical equipment that has improved the quality of life for countless people. Many people suffering from disease or disability who, in the past, were forced to make routine visits to a hospital or doctor's office for diagnostic testing currently perform diagnostic testing on themselves in the comfort of their own homes using equipment with accuracy to rival laboratory equipment.
Nonetheless, challenges in the biosensing field have remained. For example, although many diabetics currently utilize diagnostic medical equipment in the comfort of their own homes, the vast majority of such devices still require diabetics to draw their own blood and inject their own insulin. Drawing blood typically requires pricking a finger. For someone who is diagnosed with diabetes at an early age, the number of self-induced finger pricks over the course of a lifetime could easily reach into the tens of thousands. In addition, the number of insulin injections may also reach into tens of thousands. Under any circumstances, drawing blood and injecting insulin thousands of times is invasive and inconvenient at best and most likely painful and emotionally debilitating.
Some medical conditions have been amenable to automated, implantable sensing. For example, thousands of people with heart conditions have had pacemakers or defibrillators implanted into their bodies that utilize sensors for monitoring the oxygen content of their blood. Ideally, these sensors should be able to determine whether, for example, a person's heart is running very efficiently at a high heart rate or whether a person's heart has entered defibrillation. In order to effectively make this determination, an accurate sensor must be employed. Unfortunately, oxygen sensors implanted into the body have, thus far, typically required frequent and periodic checking and recalibration. In fact, one of the “holy grails” of the pacemaker industry has been an accurate, no drift, no calibration oxygen sensor. Up until now, such a sensor has been unavailable.
An ideal solution to the diagnostic requirements of those with disease or disability, absent an outright cure, is a sensor system that may be implanted into the body and that may remain in the body for extended periods of time without the need to reset or recalibrate the sensor. Regardless of the particular application for such a sensor system, in order to effect such a system the associated sensor must remain accurate, exhibit low drift and require no recalibration for extended periods of time. Such a system would typically require a sensor to be located in close proximity to sensing electronics in order to maintain the required characteristics.
However, attempts to place sensor electronics in close proximity to the sensor in implantable sensor systems have historically suffered from the environment in which they operate. For example, in an implantable sensor system for diabetics, a sensor is needed to detect an amount of glucose in the blood. Consequently, the sensor must be implanted within the body in such a manner that it comes into direct contact with the blood. However, in order to place the sensor electronics in such a system in close proximity to the sensor, the sensor electronics themselves must be placed into the blood as well. This poses obvious dangers for the sensor electronics. The sensor electronics must remain in electrical contact with the sensor; however, any exposure of the sensor electronics to the blood or any other fluid would potentially short circuit the sensor electronics and destroy the entire system.
Thus, an ideal implantable sensor system would provide for a sensor to be in close proximity to sensor electronics while also providing hermeticity between the sensor, which may be exposed to fluids, and the sensor electronics, which must remain free from short circuiting fluids. In addition, the required hermeticity must be maintained over the life of the sensing system. The present invention provides such a system.